Apparatus and Method for Regulating a Delivery Volume of a Displacement Pump

ABSTRACT

Apparatus for regulating delivery volume of a displacement pump comprises a displaceable regulating piston and a spring element acting on the regulating piston in a displacement direction (x) thereof. The apparatus further comprises a means for applying a force to the regulating piston against an effective direction (a) of the spring element.

BACKGROUND OF THE INVENTION

The invention relates to an apparatus for regulating a delivery volume of a displacement pump, the apparatus comprising a displaceable regulating piston and a spring element acting on the regulating piston in the direction of displacement thereof.

The invention also relates to a method for regulating a delivery volume of a displacement pump, such as a displacement pump comprising a suction port and a pressure port.

Displacement pumps and their regulating apparatuses are known in the art. For example, DE 10 2005 050 216 B4 discloses an apparatus for regulating the delivery volume of a displacement pump and a corresponding displacement pump. DE 10 2005 016 181 A1 describes a further regulating apparatus for a hydraulic delivery system in the form of a vane pump. A hydraulic system having a displacement pump in the form of a vane pump is known, for example, in DE 10 2008 042 728 A1. Each of these prior art documents is incorporated herein by reference in its entirety,

With such prior art apparatuses, it is possible to limit delivery volume of the variably controllable displacement pumps. For this purpose, the apparatus has a regulating piston which is displaced in its position via a differential pressure in a control pressure chamber and the force of a spring usually arranged within the control pressure chamber, so that the required pump stroke can be set, and the delivery volume of the displacement pump can be regulated automatically.

While with the prior art apparatuses and the displacement pumps controlled with them it is possible to limit the delivery volume, particularly at high speeds of a motor driving the displacement pump, this is only possible with the respective delivery volume assigned (set) to the displacement pump. In other words, based on the design of the respective displacement pump, at high speeds of a motor driving the displacement pump, the pump's delivery volume becomes constant.

It is therefore the object of the present invention to provide an apparatus for regulating the delivery volume of a displacement pump and a method for regulating the delivery volume of such a displacement pump, by means of which the delivery volume of the displacement pump can be varied to approximately any desired values.

SUMMARY OF THE INVENTION

According to the invention, due to a means for applying a force to the regulating piston against the effective direction of the spring element, it is possible to change the position of the regulating piston and thus the control variable for the delivery volume of the displacement pump, which depends on the differential pressure applied to the regulating piston and the force of the spring element. This active intervention, in which an additional force is applied to the spring element, can change the control variable on which the control is based, and thus actively vary (reduce or increase) the delivery volume of the displacement pump.

In contrast to prior known solutions, in which the delivery volume of the displacement pump could be limited with the increasing speed of the displacement pump only to the delivery volume assigned to the respective displacement pump, with the solution according to the invention it is possible to actively change the delivery volume of the displacement pump, in particular to reduce it even more or, if necessary, to increase it. A lower delivery volume of the displacement pump leads to a lower internal resistance of the displacement pump, which reduces the energy consumption caused by the displacement pump. By reducing the delivery volume, a considerable energy saving can thus advantageously be achieved.

A further significant advantage of the solution according to the invention is that the means for applying the force to the regulating piston can be retrofitted without major intervention on the displacement pump, so that the apparatus according to the invention can also he used with existing displacement pumps. This low expenditure for the apparatus according to the invention leads to comparatively low costs for the solution according to the invention.

In a very advantageous further embodiment of the invention, it may be provided that the means for applying a force to the regulating piston comprises a solenoid valve. By means of such a solenoid valve, a very simple and precise control of the means for applying the force to the regulating piston is possible. The retrofitting of a solenoid valve to existing displacement pumps can also be realized in a very simple manner.

In this respect, a very simple connection of the solenoid valve to the regulating piston can be achieve, if, for example, the solenoid valve comprises a rod which is movable in the displacement direction of the regulating piston and acts on the regulating piston.

As an alternative to the use of a solenoid valve, it is also possible that the means for applying a force to the regulating piston comprises a pneumatic valve.

Another possibility for applying the force to the regulating piston is that the means for applying a force to the regulating piston comprises a hydraulic valve.

Furthermore, it may be provided that the means for applying a force to the regulating piston comprises an electric motor.

In a further alternative embodiment of the invention, it may be provided that the means for applying a force to the regulating piston comprises a second spring element.

A typical displacement pump comprises a suction port and a pressure port. Using the apparatus according to the invention, such a displacement pump can be used, for example, in motor vehicles as a power steering pump, the regulation of its delivery volume according to the invention making it possible to save energy, for example in the form of fuel.

It has proved advantageous in particular for use in motor vehicles, if the displacement pump is designed as a vane pump.

In the invented method, a force is applied to the regulating piston against the effective direction of the spring element acting on the regulating piston, whereby the basically present variable delivery volume of the displacement pump can additionally be actively influenced.

By means of the method according to the invention, the position of the regulating piston, which is decisive for regulating the delivery volume of the displacement pump, can be changed in a very simple way, and in this way an active control of the delivery volume can be achieved. In this way, the delivery volume of the displacement pump can be influenced more strongly than before and, for example, in the case of a reduction of the delivery volume, a considerable energy saving can be achieved.

BRIEF DESCRIPTION OF DRAWINGS

The illustrated embodiments of the subject matter will be best understood by reference to the drawings, wherein like parts may be designated by like numerals throughout. The following description is intended only by way of example, and simply illustrates certain selected embodiments of devices, systems, and processes that are consistent with the subject matter as claimed herein.

FIG. 1 shows a section through a displacement pump with an apparatus according to an embodiment of the invention arranged thereon for regulating the delivery volume of the displacement pump.

FIG. 2 shows a characteristic curve of a displacement pump known from the prior art.

FIG. 3 shows a characteristic curve of a displacement pump according to an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 shows a displacement pump 1 the main features of which are known for

example from DE 10 2008 042 728 A1 and which in the present case is designed as a vane pump. Since the basic design and mode of operation of the displacement pump 1 are therefore known, they are not described in detail here.

The displacement pump 1 has a suction port and a pressure port, which are not visible in the sectional view according to FIG. 1 . The positions of the suction port and the pressure port, however, are readily known and understood by person of ordinary skill in the art, Furthermore, the displacement pump 1 has, in a manner known in the art, a housing 2 with an outer ring 3 which is movable relative to the housing 2 and an inner ring 4 which is arranged inside the outer ring 3 and is mounted on a rotational axis 5 which is stationary relative to the housing 2 and which is designed as a drive shaft. In a manner also known in the art, the inner ring 4 has a plurality of vanes 4a.

By displacing the outer ring 3 within the housing 2, the delivery volume delivered by the displacement pump 1 is changed in a manner known in the art. Since this change in the delivery volume due to the displacement of the outer ring 3 within the housing 2 is known in the art, it will not be discussed in more detail here.

An apparatus 6 is used to regulate the delivery volume, which has a regulating piston 7 that is mounted in such a way that it can be displaced in a displacement direction designated “x” within a recess 8 of the housing 2. Furthermore, the apparatus 6 has a spring element 9 acting on the regulating piston 7 in an effective direction “a”. In a manner known in the art, the position of the regulating piston 7 inside the recess 8 determines the pressure acting on the outer ring 3 and thus adjusts the position of the outer ring 3.

The regulating piston 7 is therefore mounted within the recess 8 in such a way that it can be moved in two directions (back and forth) in accordance with the double arrow “x”. While the effective direction “a” of the spring element 9 is parallel to the direction of displacement x of the regulating piston 7, due to the nature of the spring element 9, which can only apply force in one direction, it only runs in one direction,

The apparatus 6 for regulating the delivery volume of the displacement pump 1 furthermore comprises means 10 for applying a force to the regulating piston 7 in the direction opposite to the effective direction a of the spring element 9, i.e., in the direction opposite to the arrow “a”.

By applying force to the regulating piston 7 by means of the means 10, it is possible to change the position of the regulating piston 7 within the recess 8. The means 10 is thus not only able to apply a force to the regulating piston 7, but is able to change the position of the regulating piston 7. This change in the position of the regulating piston 7 causes a change in the position of the outer ring 3 within the housing 2, and thus causing a change in the delivery volume of the displacement pump 1.

The force applied by the means 10 to the regulating piston 7 is constantly applied as long as a certain delivery volume of the displacement pump 1 is to be set, in order to lock the desired position of the regulating piston 7.

FIGS. 2 and 3 show the effect of the means 10 for applying the force to the regulating piston 7. While FIG. 2 shows the displacement volume FV of a displacement pump known from the prior art over the rotational frequency n, FIG. 3 shows the displacement volume FV of the displacement pump 1 according to the invention over the rotational frequency n.

It can be seen from the two parallel, horizontal lines in FIG. 3 that an actively variable displacement volume FV of the displacement pump 1 is possible in a region between them, designated by the reference sign 11, i.e., that the displacement volume FV of the displacement pump 1 can be actively affected in this region 11 by applying the force to the regulating piston 7 against the effective direction “a” of the spring element 9. The point at which the constant delivery volume changes into a variable delivery volume can be influenced by selecting a spring constant of the spring element 9.

Control of the means 10 can be effected via a control device (not shown), for example a part of a motor vehicle in whose steering system the displacement pump 1 is installed.

In one embodiment of the invention, the means 10 for applying the force to the regulating piston 7 has a solenoid valve 12. The solenoid valve 12 in turn has a rod 13 which is movable in the displacement direction “x” of the regulating piston 7 and acts on the regulating piston 7. The rod 13 is preferably sealed off from the housing 2 by means of suitable sealing elements, so that hydraulic medium located inside the recess 8 cannot escape through the area in which the rod 13 enters the housing 2.

In other embodiments of the invented apparatus 6, the means 10 for applying the force to the regulating piston 7 can also comprise a pneumatic valve, a hydraulic valve, an electric motor and/or a second spring element.

Although the disclosure is described herein with reference to specific embodiments, various modifications and changes can be made without departing from the scope of the present disclosure as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of the present disclosure. Any benefits, advantages, or solutions to problems that are described herein with regard to specific embodiments are not intended to be construed as a critical, required, or essential feature or element of any or all the claims.

Because individual structures for performing the various steps of the invented method are believe to be understandable to one skilled in the art, further details of the individual steps are not necessary for making and using the invention.

Unless otherwise stated, conditional terms such as “can,” “could,”, “will,” “might,” or “may” are understood within the context as used in general to convey that certain embodiments include, while other embodiments do not include, certain features and/or elements. Thus, such conditional terms are not generally intended to imply that features and/or elements are in any way required for one or more embodiments.

It will be understood by those within the art that, in general, terms used herein, are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). 

1. An apparatus for regulating a delivery volume of a displacement pump, the apparatus comprising: a displaceable regulating piston; a spring element acting on the regulating piston in a displacement direction of the regulating piston; and a means for applying a force to the regulating piston against an effective direction of the spring element.
 2. The apparatus of claim 1, wherein the means for applying a force to the regulating piston comprises a solenoid valve.
 3. The apparatus of claim 2, wherein the solenoid valve comprises a rod that is movable in the displacement direction of the regulating piston and acts on the regulating piston.
 4. The apparatus of claim 1, wherein the means for applying a force to the regulating piston comprises a pneumatic valve.
 5. The apparatus of claim 1, wherein the means for applying a force to the regulating piston comprises a hydraulic valve,
 6. The apparatus of claim 1, wherein the means for applying a force to the regulating piston comprises an electric motor.
 7. The apparatus of claim 1, wherein the means for applying a force to the regulating piston comprises a second spring element.
 8. A system comprising: a displacement pump comprising a suction port and a pressure port; and an apparatus coupled to the displacement pump for regulating a delivery volume of the displacement pump, the apparatus comprising: a displaceable regulating piston; a spring element acting on the regulating piston in a displacement direction of the regulating piston; and a means for applying a force to the regulating piston against an effective direction of the spring element.
 9. The system of claim 8, wherein the means for applying a force to the regulating piston comprises a solenoid valve.
 10. The system of claim 9, wherein the solenoid valve comprises a rod that is movable in the displacement direction of the regulating piston and acts on the regulating piston.
 11. The system of claim 8, wherein the means for applying a force to the regulating piston comprises a pneumatic valve.
 12. The system of claim 8, wherein the means for applying a force to the regulating piston comprises a hydraulic valve.
 13. The system of claim 8, wherein the means for applying a force to the regulating piston comprises an electric motor.
 14. The system of claim 8, wherein the means for applying a force to the regulating piston comprises a second spring element.
 15. The system of claim 8, wherein the displacement pump is a vane pump.
 16. A method for regulating a delivery volume of a displacement pump, the method comprising the step of applying a force to a regulating piston against an effective direction of a spring element, wherein the spring element acts on the regulating piston in a displacement direction of the regulating piston. 